1. Technical Field
The invention relates to a patch antenna device and antenna device that may be used in a handy terminal for reading a UHF RFID, or the like.
2. Background Art
A patch antenna device includes a ground electrode made of a conductor, a dielectric substrate mounted on the ground electrode, and a conductive radiation electrode formed on the dielectric substrate. The patch antenna device thus configured patch antenna device not only may be reduced in thickness and is able to achieve high gain but also is compatible with an unbalanced circuit, such as a coaxial line or a microstrip line and, therefore, has many advantages, for example, in that it is possible to easily achieve matching with these circuits. For the above reason, the patch antenna device is widely used in an RFID handy terminal and other types of transceiver (for example, see Patent Document 1).
In addition, as a type of antenna device, an array antenna device has been suggested, in which a plurality of patch antenna devices are used as patch antenna elements (for example, see Patent Document 2). The above array antenna device generally has a planar structure. That is, a multiple number of radiation electrodes are arranged on a wide front surface of one dielectric substrate in a planar manner, a coaxial cable is connected from the rear surface side of the dielectric substrate to each radiation electrode, and then an RF signal from a power supply unit is supplied through the coaxial cable to each radiation electrode. Alternatively, a strip line is provided on the rear surface, or the like, of the dielectric substrate, and then an RF signal from the power supply unit is electromagnetically coupled through the strip line to each radiation electrode. Thus, radio waves from the radiation electrodes are radiated in a front (forward) direction perpendicular to the front surface of the dielectric substrate.    Patent Document 1: Japanese Unexamined Patent Application Publication No. 2006-245751    Patent Document 2: Japanese Unexamined Patent Application Publication No. 2001-111336